Periphyton-based water quality analysis of a large river (River Danube, Hungary): exploring the potential of molecular fingerprinting for biomonitoring

Abstract

Water quality monitoring based on microscopical analysis of periphytic algae is fundamental to the European Water Framework Directive. However, the outcome of this kind of monitoring is often dependent on the experience of the operating taxonomist and the availability of an electron microscope for fine-scale taxonomic analysis. Furthermore, it is hampered by the insufficiencies of the morphology-based diatom taxonomy. Molecular fingerprinting methods have the potential to evade these problems and serve as a complementary tool in biomonitoring studies. To test this concept, periphyton of the River Danube was monitored for a period of six months using microscopical and molecular fingerprinting (terminal restriction fragment length polymorphism) methods in parallel. We identified 120 diatom taxa by light and electron microscopy, and diatom-based water quality using Omnidia Version 4 software was found to be good or moderate (IPS value between 12 and 16). The number of operational taxonomic units identified by terminal restriction fragment length polymorphism analysis of the 18S rRNA gene ranged from 7 to 29 for individual samples, and was in total 88 in the Mspl digest and 33 in the Rsal digest. The results of both analyses were compared by hierarchical classification and we found good correlation between the two methods. We propose, that after further development of molecular databases and methodology, molecular fingerprinting may have the potential to be implemented for routine biomonitoring purposes.